Conversion of ammonia into nitrate is sensitive to a number of inhibitors. There is limited information on the nitrification inhibition coefficient and mathematical models in the current literature. The nickel inhibition constant was found in nitrogen removal using an activated sludge system. In the first set of experiments, nickel-free wastewater was used to determine the optimum operating conditions. In the second set of experiments, the effect of the nickel concentration on the system performance was investigated. The ammonium removal efficiency was not affected by low Ni concentrations (< 7mg/L). When the Ni concentration was increased to 11 mg/L, the nitrification efficiency decreased by more than 45.53%.
Based on the experimental results, a mathematical model was developed, and the nickel inhibition constants (KNi) were found to be 8.75 mg/L.